[libcxx][nfc] Fix the ASAN bots: update expected.pass.cpp.

Ensures that `get_return_object`'s return type is the same as the return type for the function calling `co_return`. Otherwise, we try to construct an object, then free it, then return it.

Differential Revision: https://reviews.llvm.org/D103196

libcxx/test/std/experimental/language.support/support.coroutines/end.to.end/expected.pass.cpp

@@ -35,7 +35,7 @@ struct expected {
 
   struct promise_type {
     std::shared_ptr<Data> data;
-    std::shared_ptr<Data> get_return_object() { data = std::make_shared<Data>(); return data; }
+    expected get_return_object() { data = std::make_shared<Data>(); return {data}; }
     suspend_never initial_suspend() { return {}; }
     suspend_never final_suspend() noexcept { return {}; }
     void return_value(T v) { data->val = v; data->error = {}; }